Energetic electron beams employed for radiation therapy produce patient dose distributions that may differ significantly from the distributions predicted by conventional treatment planning calculations. It is proposed to systematically measure the bulk scattering and absorption effects of electrons impinging upon inhomogeneous media and to develop the foundation for an algorithm capable of predicting the dose to relevant locations in patients with an accuracy of plus or minus 5 percent. Initially, dose distributions near small tissue simulating inhomogeneous structures with simple geometries will be studied to understand effects of a small number of physical variables that can be conveniently measured with a computed tomographic (CT) scanner. A model that predicts these dose distributions will be formulated and generalized to account for an arbitrary arrangement of tissue in patients. The location and density of the treatment site surrounding tissue will be input into the calculation from a series of CT images.